The present invention is generally directed to photoconductive imaging members, and more specifically to photoconductive imaging members comprised of acetoxymetal phthalocyanine photogenerating pigments, such as trihaloacetoxymetal phthalocyanines like bis(trifluoroacetoxy)germanium phthalocyanine. In embodiments, the trihaloacetoxymetal phthalocyanine photogenerating pigments are obtained from the reactions of hydroxymetal phthalocyanines with a trihaloacetic acid in an inert solvent such as methylene chloride. One embodiment of the present invention is directed to an imaging member comprised of a supporting substrate, a photogenerating layer comprised of the acetoxymetal phthalocyanine pigments in contact therewith, and a charge, especially hole, transport layer. Imaging members with the photogenerating pigments of the present invention are especially sensitive to wavelengths of from about 700 to about 800 nanometers, that is in the near infrared wavelength region of the light spectrum, and these imaging members in many instances possess excellent electrical characteristics, such as low dark decay of less than 50 volts/second, and half exposure energy (E.sub.1/2) of less than about 5 ergs/cm.sup.2 when exposed to monochromatic radiation of about 700 to about 800 nanometers, thus enabling use thereof in imaging systems with high speeds, for example exceeding 50 pages per minutes, and with excellent cycling characteristics, thereby permitting the photoconductive imaging members with these pigments to be selected for use in electrophotographic imaging processes, and the like, in which infrared or near infrared radiations are utilized to discharge the surface potential of photoconductive imaging members.
Certain photoconductive imaging members are known, such as those comprised of a homogeneous layer of a single material such as vitreous selenium, or composite layered devices containing a dispersion of a photoconductive composition. An example of a composite xerographic photoconductive member is described in U.S. Pat. No. 3,121,006, which discloses finely divided particles of a photoconductive inorganic compound dispersed in an electrically insulating organic resin binder.
Photoconductive imaging members comprising inorganic or organic materials wherein the charge generating and charge transport functions are performed by discrete contiguous layers are also known. Additionally, layered photoconductive imaging members are disclosed in the prior art, including members with an overcoat layer of an electrically insulating polymeric material. Other layered photoconductive devices have been disclosed, including those comprising separate photogenerating layers and charge transport layers as described in U.S. Pat. No. 4,265,990, the disclosure of which is totally incorporated herein by reference. Photoresponsive materials containing a hole injecting layer overcoated with a hole transport layer, followed by an overcoating of a photogenerating layer, and a top coating of an insulating organic resin are disclosed in U.S. Pat. No. 4,251,612, the disclosure of which is totally incorporated herein by reference. Examples of photogenerating layers disclosed in these patents include trigonal selenium and phthalocyanines, while examples of transport layers include certain aryl diamines as illustrated therein.
Imaging members with certain phthalocyanines, such as metal phthalocyanines like titanyl phthalocyanine, vanadyl phthalocyanine, hydroxygallium phthalocyanine, or dihydroxygermanium phthalocyanine, are known. Some of the aforementioned imaging members possess photosensitivity in the near infrared region of the spectrum. However, many of these photogenerating pigments exhibit a variety of polymorphic forms with vastly different photosensitivities. These polymorphic forms are often sensitive to the process conditions under which the photoresponsive imaging members are fabricated. For example, the transformation of one polymorphic form to another may occur when the pigment is subjected to ball milling or simply being brought into contact with a certain solvent. This polymorphic transformation generally leads to changes in the pigment's photosensitivity and cyclic stability, and may result in the imaging member not meeting the performance requirements and specifications. The photogenerating pigments of the present invention are believed to be stable to a variety of fabrication conditions, and their photoconductivities are not affected by the fabrication processes. In addition, the acetoxymetal phthalocyanines can be readily prepared from the corresponding hydroxymetal phthalocyanines by simple processes, generally without lengthy post-reaction purification procedures.
U.S. Pat. No. 3,574,181 discloses bisazo compounds useful as coloring agents. Composite electrophotographic photosensitive materials containing various azo compounds are disclosed in U.S. Pat. No. 4,618,672, wherein bisazo compounds particularly suitable for use in the charge generating layer of a layered electrophotographic photoconductor are illustrated.
U.S. Pat. No. 4,7113,307, the disclosure of which is hereby totally incorporated by reference, also discloses photoconductive imaging members containing a supporting substrate, certain azo pigments as photogenerating materials, and a hole transport layer that preferably contains an aryl diamine compound dispersed in an inactive resinous binder.
U.S. Pat. No. 4,797,337, the disclosure of which is totally incorporated herein by reference, discloses a photoconductive imaging member comprising a supporting substrate., a hole transport layer, and a photogenerating layer comprising specific bisazo compounds.
Documents illustrating layered organic electrophotographic photoconductor elements with azo, bisazo, and related compounds include U.S. Pat. Nos. 4,390,611, 4,551,404, 4,596,754, 4,400,455, 4,390,608, 4,327,168, 4,299,896, 4,314,015, 4,486,522, 4,486,519, 4,555,667, 4,440,845, 4,486,800, 4,309,611, 4,418,133, 4,293,628, 4,427,753, 4,495,264, 4,359,513, 3,898,084, 4,830,944, and 4,820,602.
U.S. Pat. No. 4,424,266 discloses an electrophotographic photosensitive element having a conductive support and a photosensitive layer comprising a carrier generating phase layer containing a carrier generating material selected from the group consisting of perylene dyes, polycyclic quinones and azo dyes, and a carrier transporting phase layer containing a hydrazone carrier transporting material. The carrier generator materials can be used either singly or in combination.
In a copending application U.S. Ser. No. 105,264 preparative processes for dihydroxygermanium phthalocyanine photogenerating pigment, and its conversion to a Type II polymorphic form are disclosed. Another copending application U.S. Ser. No. 228,619 describes the preparation of Type III polymorph of dihydroxygermanium phthalocyanine and its use in infrared-responsive layered photoconductive imaging members. The disclosures of each of the aforementioned copending applications are totally incorporated herein by reference.
Although these known imaging members are suitable for their intended purposes, a need remains for improved imaging members that would satisfy a variety of performance requirements. For example, there is a particular need for imaging members containing photoconductive materials with improved photoconductivity. Another need resides in the provision of imaging members containing acetoxymetal phthalocyanine components, which are photoresponsive to near infrared radiations. There is also a need for imaging members with photoconductive materials comprised of certain acetoxymetal phthalocyanine photogenerating pigments, which pigments can be obtained in an electrically pure form by simple cost-effective processes. Further, there is a need for photoconductive materials with enhanced dispersibility in polymer solutions that enable low cost coating processes for the preparation of photoconductive imaging members. Additionally, there is a need for photoconductive materials that enable fabrication of imaging members with enhanced photosensitivity in the near infrared wavelength regions of the light spectrum enabling the resulting imaging members thereof to be selected for LED xerographic imaging processes and printers, and diode laser printer and imaging apparatuses.